The revelation of former President Joe Biden’s cancer diagnosis has seemed to halt the ongoing debate over his fitness for office. But the co-author of the new book “Original Sin” tells Variety that conversation is fair,

Biden's office said he had been diagnosed on Friday with "aggressive" prostate cancer that had spread to his bones. Cancers that have spread, or metastasized, are considered stage 4, the most advanced.

It’s aggressive. The cells have an ugly, disordered appearance under a microscope. Pathologists gave them a Gleason score of 9 (out of 10) for their likelihood to advance quickly. The cancer has already moved from Biden’s prostate to his bones, which means it cannot be cured — only controlled with drugs.